1. Technical Field
The present invention relates to a receiving apparatus having a clock generating section for outputting a spread clock signal which is generated by cyclically increasing and decreasing the frequency of a clock signal, to an image-forming apparatus comprising the receiving apparatus, to receiving method and to recording medium.
2. Description of Related Art
Conventional circuits for preventing EMI (Electro Magnetic Interference) of electronic equipment use methods, such as a method of filtering harmonic components of a clock signal of the electronic equipment, a method of effectively securing a return ground (GND), and a method of scattering radiation energy by spreading the spectrum of a clock signal.
The above-mentioned method of scattering radiation energy by spreading the spectrum of a clock signal is implemented by changing the frequency of the clock signal with time. A known system for changing the frequency of the clock signal with time is an analog system using a PLL (Phase Locked Loop) or a digital system using a variable delay circuit (variable delay line).
Patent Document 1 (see Japanese Patent Application Laid-Open No. 2001-268355) discloses an image-reading apparatus which, when modulating a drive clock in photoelectric converting means and an analog process by a spread spectrum clock signal (hereinafter referred to as the spread clock signal), aligns the phases of modulation cycles of the spread spectrum clock signal in accordance with a main scanning line signal LSYNC to match the phases of modulation frequencies, thereby making cyclic noise in a main scanning line equal to that in the following main scanning lines and enabling removal of noise by the shading processing means in the later stage to meet EMI regulations.